From the publication "Cyclical Maintenance for Historic Buildings",
by J. Henry Chambers, AIA, National Park Service - Office of
Archeology and Historic Preservation, 1976.

This standard includes a list of miscellaneous maintenance tasks
along with estimated performance times required for completing each
task. These figures may be used to estimate the amount of time
required to perform a group of tasks; however, they are based on
estimations for commercial and industrial structures and may need
to be adjusted for applications in historic buildings. Therefore,
local estimates should be adjusted based on observation and
experience.

Frequency of tasks should be analyzed prior to determining the
total performance time for a group of tasks. Outside contractors
should be employed when maintenance tasks require special skills,
expensive equipment or tools and materials that are not readily
available. These more complex tasks should be omitted from any
calculations involving in-house employees.

Results of these calculations may be used for planning purposes to
calculate staff size which can be adjusted based on specific needs.
Assume 2000 man-hours/year for the average full-time employee.
Once the time required for performing a group of maintenance tasks
has been calculated, staff size can be determined by dividing the
maintenance time (in hours) by 2000 man-hours.

Add additional time to the total work time determined for a group
of tasks for room preparation (i.e. moving, stacking and returning
furniture back to its original location) and for assembly, set-up
and clean-up of equipment used.

For sample time estimate forms and additional information relating
to maintenance, see the publication "Cyclical Maintenance for
Historic Buildings".